Prompt: Write a short story about a man who discovers a magical portal

Gregorio entered the portal with a feeling of excitement. He had been searching for this for years. It was supposed to lead to the most important discovery of his life. As he stepped through the door, he felt a sudden sense of movement and then he was lost in the darkness. He tried to turn back but he was suddenly overwhelmed by a force that prevented him from moving. He felt like he was drowning and then he blacked out.